Thirty-six-cornered strengthening member

ABSTRACT

A strengthening member for an automotive vehicle includes a thirty-six-cornered cross section having adjacent sides defining internal angles and external angles. Each of the internal angles and the external angles are at least 45 degrees and are less than 180 degrees. The sides define a plurality of adjacent lobes disposed about a perimeter of the strengthening member. Along the perimeter of the thirty-six-cornered cross section, individual lobes of the plurality of lobes are separated by one external angle.

TECHNICAL FIELD

This disclosure relates generally to vehicle structures, and moreparticularly to a strengthening member for a vehicle body or otherstructures, and more particularly to a strengthening member having athirty-six-cornered cross section.

BACKGROUND

Vehicle strengthening members may be used to increase load carryingcapacity, impact energy absorption, and bending resistance whilereducing mass per unit length of the strengthening member.

When a compressive force is exerted longitudinally on a strengtheningmember (for example, a force due to a front impact load on a vehicle'sfront rail or other strengthening member in the engine compartment), thestrengthening member may crush in a longitudinal direction to absorb theenergy of the collision. In addition, when a bending force is exerted ona strengthening member (for example, a force due to a side impact loadon a vehicle's front side sill, B-pillar or other strengthening member),the strengthening member may bend to absorb the energy of the collision.

Under axial loading conditions, axial collapse of a strengthening membermay proceed in an unstable buckling mode that is initiated in a middleof the strengthening member before moving to a top of the strengtheningmember in a non-progressive manner. An unstable collapse mode mayincrease the variation in crash behaviors among replicate samples andmay make crash performance more difficult to predict. An unstablecollapse mode may also absorb less impact energy and may be lessefficient in material utilization compared to a progressive and stablecollapse mode.

SUMMARY

A strengthening member for an automotive vehicle includes athirty-six-cornered cross section having adjacent sides defininginternal angles and external angles. Each of the internal angles and theexternal angles are at least 45 degrees and are less than 180 degrees.The sides define a plurality of adjacent lobes disposed about aperimeter of the strengthening member. Along the perimeter of thethirty-six-cornered cross section, individual lobes of the plurality oflobes are separated by one external angle.

A method for manufacturing a strengthening member for an automotivevehicle includes fabricating two or more sections of the strengtheningmember. The method further includes joining the two or more sections toform the strengthening member having the thirty-six-cornered crosssection. The thirty-six-cornered cross section includes twenty-fourinternal angles and twelve external angles disposed between thirty-sixsides.

A strengthening member for an automotive vehicle includes athirty-six-cornered cross section having thirty-six sides and definingtwenty-four internal angles and twelve external angles. The crosssection defines four adjacent lobes disposed about a central axis. Eachlobe defines six internal angles and two external angles. Along aperimeter of the cross section, adjacent lobes define one external angledisposed therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary thirty-six-cornered cross section,having twenty-four internal angles and eight external angles, for astrengthening member.

FIGS. 2A-2F illustrate how tunable parameters in accordance with thepresent disclosure can be utilized to modulate the cross section of FIG.1.

FIG. 3 illustrates strengthening members of varying cross sectionshaving substantially the same thickness, length, and perimeter.

FIG. 4 illustrates an exemplary axial collapse of the strengtheningmembers shown in FIG. 3.

FIG. 5 illustrates an exemplary dynamic crush of the strengtheningmembers shown in FIG. 3.

FIG. 6 is a graph of the crush force and associated axial crush distancefor exemplary strengthening members having the cross sections shown inFIG. 3.

FIG. 7 is a graph of the axial crush energy and associated axial crushdistance for exemplary strengthening members having the cross sectionsshown in FIG. 3.

FIGS. 8A and 8B illustrate exemplary thirty-six-cornered cross sections,having twenty-four internal angles and twelve external angles, for astrengthening member.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments may take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures may be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

The present disclosure describes a strengthening member with athirty-six-cornered cross section having a substantially increasedstiffness throughout the sides and corners without increasing thicknesswithin the corners. The strengthening member provides, for example, avariety of tunable parameters configured to achieve strength increases(i.e., load carrying and energy absorption) over basic polygonal designs(e.g., polygonal strengthening member cross sections having less or thesame number of sides), while also allowing design flexibility to meet arange of vehicle applications. The strengthening member can achieveincreased energy absorption and a more stable axial collapse when forcessuch as front and side impact forces are exerted on the strengtheningmember. The strengthening member may also possess improved durabilityand noise-vibration-harshness (NVH) performance due to work hardening onthe thirty-six corners. Furthermore, the side lengths andconfigurations, and/or degrees of the internal and external angles, ofthe present disclosure can achieve a similar, if not greater, strengthincrease as thickened corners, while minimizing mass per unit length ofthe member and maintaining a high manufacturing feasibility.

Conventional strengthening members having basic polygonal crosssections, such as, square, rectangular, hexagonal and octagonal, etc.,are generally used due to their manufacturing feasibility. Becausestrengthening members with multi-cornered cross sections in accordancewith the present disclosure have substantially increased strength andstiffness without requiring thicker corner portions, they also have ahigher manufacturing feasibility than previously-contemplated membersthat have thickened corners. While still providing a desired strength, astrengthening member in accordance with the present teachings can beformed in one or multiple sections by, for example, bending, rolling,cutting, forging, stamping, press forming, hydro-forming, molding, diecasting, and extrusion. Thus-formed sections can be joined via welding,adhesive, fastening, or other known joining technologies.

A strengthening member can comprise, for example, steel alloys, aluminumalloys, magnesium alloys, titanium alloys, nylons, plastics, polymers,fiber-reinforced composites, silicone, semiconductor, papers, hybridmaterials (e.g., multiple dissimilar materials), shape-memory materials,forms, gels or any other suitable materials. Those of ordinary skill inthe art would understand, for example, that the material used for astrengthening member may be chosen as desired based on intendedapplication, strength/weight considerations, cost, and other designfactors.

A thirty-six-cornered cross section in accordance with the presentdisclosure is contemplated for use with a number of structural memberssuch as a front rail, a side rail, a cross member, roof structures,shotguns, beltline tubes, door beams, pillars, internal reinforcements,and other components that can benefit from increased load carryingcapacity, crash energy absorption, and bending resistance. In addition,the present teachings can be applied to both body-on-frame and unitizedvehicles, or other types of structures.

Referring now to FIG. 1, a strengthening member may be provided with athirty-six-cornered cross section. As illustrated, the cross sectioncomprises thirty-six sides having lengths S₁-S₃₆ and thicknesses T₁-T₃₆,twenty-four internal corners with angles θi₁-θi₂₄ and twelve externalcorners with angles θe₁-θe₁₂. The side lengths and thicknesses andinternal and external corner angles can be varied (i.e., tuned) toachieve improved strength and other performance features (e.g.,stability of folding pattern) compared to existing strengthening membercross sections. This strength improvement may further obviate the needfor increased corner thickness, which is an unexpected and unpredictedbenefit of fine-tuning the design parameters (e.g., side lengths,thicknesses, internal angles, and external angles) of a strengtheningmember having a thirty-six-sided (i.e., thirty-six-cornered) crosssection.

As shown in FIGS. 2A-2E, for example, in accordance with variousapproaches, the lengths S₁-S₃₆ (see FIGS. 2C-2E) and thicknesses T₁-T₃₆(see FIG. 2B showing tapered sides) of the sides and the angles θi₁-θi₂₄of the internal angles may be varied, as would be understood by oneskilled in the art, for example in accordance with available packagingspace within a vehicle. Those of ordinary skill in the art wouldunderstand, however, that FIGS. 2A-2E are exemplary only, and areprovided merely to illustrate how design parameters can be utilized tomodulate the cross section of the exemplary approach of FIG. 2. Forexample, angles θe₁-θe₁₂ of the external angles may also be varied, aswould be understood by one skilled in the art. Thus, the presentdisclosure contemplates various thirty-six-cornered cross sectionconfigurations having various shapes and dimensions (i.e., corner bendradii, side lengths, thicknesses, internal angles and/or externalangles), which can be adjusted based on space requirements and/or tocontrol member collapse modes.

In certain approaches, for example, a length of each side (S₁-S₃₆) canrange from about 10 mm to about 250 mm. In other exemplary approaches,such as in aircrafts, spacecrafts, watercrafts, high-speed railvehicles, or building applications, for example, a length of each side(S₁-S₃₆) may be larger. In certain additional approaches, a thickness ofthe sides and corners can range from about 0.7 mm to about 6.0 mm; andin certain approaches, the thickness of the sides is substantially thesame as the thickness of the corners. In other exemplary approaches,such as in aircrafts, spacecrafts, watercrafts, high-speed railvehicles, or building applications, for example, the thickness of theside may be larger. Furthermore, in accordance with certain additionalexemplary approaches, the thickness of the strengthening member mayvary, for example, within one side or from side to side to optimize theoverall axial crush and bending performance. The lengths S₁-S₃₆ andthicknesses T₁-T₃₆ of the sides can be varied to a certain degree, aswould be understood by one skilled in the art, for example in accordancewith available packaging space within a vehicle.

In certain approaches, each of the internal angles and the externalangles are at least 45 degrees and are less than 180 degrees. Forexample, internal angles θi₁-θi₂₄ may range from about 45 degrees toabout 170 degrees, and external angles θe₁-θe₁₂ may range from about 45degrees to about 120 degrees (e.g, approximately 90 degrees). In oneapproach, certain internal angles (e.g., θi₃, θi₆, θi₉, θi₁₂, θi₁₅,θi₁₈, θi₂₁, and θi₂₄) may be approximately 90 degrees, and otherinternal angles (e.g., θi₁, θi₂, θi₄, θi₅, θi₇, θi₈, θi₁₀, θi₁₁, θi₁₃,θi₁₄, θi₁₆, θi₁₇, θi₁₉, θi₂₀, θi₂₂, and θi₂₃) may be greater than 90degrees (e.g., approximately 135 degrees).

The thirty-six-cornered cross section defines a plurality of lobesdisposed about a perimeter of the strengthening member. Moreparticularly sides of the cross section may define internal angles andexternal angles that form the lobes. For example, as shown in FIG. 1,sides S₄-S₁₂ may form internal angles θi₂-θi₇ and external angles θe₃and θe₄ to thereby define a first lobe. Sides S₁₃-S₂₁ may form internalangles θi₈-θi₁₃ and external angles θe₆ and θe₇ to thereby define asecond lobe. Sides S₂₂-S₃₀ may form internal angles θi₁₄-θi₁₉ andexternal angles θe₉ and θe₁₀ to thereby define a third lobe. SidesS₃₁-S₃₆ and sides S₁-S₃ may form internal angles θi₂₀-θi₂₄ and θi₁ andexternal angles θe₁₂ and θe₁ to thereby define a fourth lobe. Thus,individual lobes of the plurality of lobes may include six internalangles and two external angles defined by nine sides. The individuallobes may be connected to adjacent individual lobes to form externalangles θe₂, θe₅, θe₈, and θe₁₁ therebetween. Although four lobes aredescribed herein, other combinations of sides and internal angles mayresult in more or less lobes.

Furthermore, individual lobes of the plurality of lobes may include afirst side wall (e.g., distal side wall S₈) extending in a planeparallel to a first axis, two side walls (e.g., side walls S₄ and S₁₂)extending in planes parallel to a second axis that is perpendicular tothe first axis, and six side walls (e.g., side walls S₅, S₆, S₇, S₉,S₁₀, and S₁₁) extending in planes disposed at a non-zero angle relativeto the first axis. For example, the non-zero angle may be approximately45 degrees. In this way, the angled side walls may define a first set ofparallel walls (e.g., side walls S₅, S₇, and S₁₀) and a second set ofparallel walls (e.g., side walls S₆S₉, and S₁₁) that extendperpendicular to the first set of parallel walls.

Individual lobes of the plurality of lobes may be separated by one ormore external angles. In one approach, an individual lobe may beseparated from an adjacent lobe by one external angle. With reference toFIG. 1, external angle θe₂ (defined by sides S₃ and S₄) may separate afirst lobe from a second lobe. Thus, the individual lobes may beseparated by only external angles, with no internal angles disposedtherebetween. In still other approaches, the cross section may beprovided with internal angles between adjacent lobes.

The lobes may be disposed about a central axis of the strengtheningmember around the perimeter of the strengthening member. In oneapproach, shown for example in FIGS. 2A, 2B, 2D, 2E, and 2F, side wallsof the lobes are evenly spaced about the central axis. In anotherapproach, shown for example in FIG. 2C, side walls of the lobes may beunevenly spaced about the central axis. In this approach, the crosssection of the strengthening member may be provided with a 10/7 aspectratio, as compared to the cross sections of FIGS. 2A, 2B, 2D, 2E, and2F. As shown in FIG. 2C, a first side wall of a first lobe may be spaceda first distance from a second side wall of a second lobe adjacent tothe first lobe along the perimeter. A third side wall of the first lobemay be spaced a second distance from a fourth side wall of a third lobeadjacent to the first lobe along the perimeter. In this approach, thefirst and second distances have different lengths. For example, thefirst distance may be greater than the second distance.

As shown in FIG. 2F, the thirty-six-cornered cross section may definerelatively a shallow recess design. In this approach, internal and/orexternal angles can be less than 90 degrees (e.g. approximately 45degrees).

In comparing crash energy absorption of strengthening members of varyingshapes having the same thickness and perimeter, as illustrated in FIG.3, for example for an impact with a rigid wall at 35 mph, athirty-six-cornered cross section in accordance with the presentdisclosure may result in a shorter crush distance and smaller foldinglength. The thirty-six-cornered cross section may also provide improvedaxial collapse stability and improved crash energy absorption. Forexample, a thirty-six-cornered cross section in accordance with thepresent disclosure may achieve about a 100-150% increase in crash energyabsorption over a square cross section and a 90-115% increase in crashenergy absorption over hexagonal and octagonal cross sections.

To demonstrate the improved strength and performance features of athirty-six-cornered cross section in accordance with the presentdisclosure compared to various existing cross section designs, exemplarystrengthening members were modeled and experimental test runs wereconducted, as shown and described below with reference to FIGS. 3-7.

Strengthening members of varying shapes (i.e., cross sections) havingthe same thickness, length and perimeter (e.g., each part having a massof about 1.22 Kg) were modeled as illustrated in FIG. 3. Tests were thenrun for each member to simulate an impact with the same rigid mass (e.g.an impactor), impact speed, and initial kinetic energy. As shown in FIG.4, the thirty-six-cornered cross section in accordance with the presentdisclosure demonstrated the most stable axial collapse and the highestcrash energy absorption. Furthermore, as shown in FIG. 5, thethirty-six-cornered cross section in accordance with the presentdisclosure also demonstrated the shortest crush distance and smallestfolding length.

FIG. 6 illustrates the crush force (in KN) and associated axial crushdistance (in mm) for the simulated impact, exerted axially on theexemplary strengthening members having the cross sections shown in FIG.3. As shown in FIG. 6, the strengthening member having athirty-six-cornered cross section could sustain a much higher crushingforce for a given resulting crushing distance as compared with thesquare, hexagonal, circular and octagonal cross sections. This allowsimproved impact energy management while minimizing mass per unit length.

FIG. 7 illustrates the axial crush energy (in KN-mm) and associatedaxial crush distance (in mm) for the exemplary strengthening membershaving the cross sections shown in FIG. 3. As shown in FIG. 7, thestrengthening member having a thirty-six-cornered cross section couldabsorb the total kinetic energy of the impact (i.e., 22,983 Kn-mm) overa much shorter distance as compared with the square, hexagonal, circularand octagonal cross sections.

Referring now to FIGS. 8A and 8B, a strengthening member may be providedwith a thirty-six-cornered cross section. In the approaches of FIGS. 8Aand 8B, the thirty-six-cornered cross section defines twenty-fourinternal angles and twelve external angles. As shown, the twenty-fourinternal angles may be greater than 90 degrees. In the approach shown inFIG. 8A, certain external angles (e.g, eight external angles) may begreater than 90 degrees (e.g., 135 degrees), and certain other externalangles (e.g., four external angles) may be approximately 90 degrees. Inthe approach shown in FIG. 8B, all external angles are greater than 90degrees. For example, certain external angles (e.g, eight externalangles) may be approximately 135 degrees, and certain other externalangles (e.g., four external angles) may be approximately 110-115degrees. The strengthening member may define a continuous taper along asubstantial length of the strengthening member from a first end of thestrengthening member to a second end of the strengthening member.

In many approaches, the strengthening member may be disposed at anexterior of a vehicle, and therefore may be exposed to moisture andother elements such as rain, snow, salt, mud, etc. Such elements maycause corrosion problems, particularly, for example, in accumulationregions such as recesses or indentations. The strengthening membersaccording to FIGS. 8A and 8B may provide improved moisture shedding ascompared to known strengthening members. For example, increasing theexternal angles to greater than 90 degrees increases the contact angleof moisture contacting the strengthening member at the external angle,thereby increasing the hydrophobicity of the strengthening member at theexternal angle. In this way, a strengthening member (e.g., astrengthening member disposed at an exterior of a vehicle) that may beexposed to moisture may be provided with improved moisture sheddingcapabilities.

A method for manufacturing a strengthening member for an automotivevehicle may include fabricating two or more sections of thestrengthening member. Fabricating the two or more sections may includestamping, press forming, roll forming, hydroforming, molding, casting,machining, forging, 3-D printing, and/or extruding each of the two ormore sections.

The method may further include joining the two or more sections to formthe strengthening member having the thirty-six-cornered cross section.The two or more sections may be joined by one or more of welding,adhesion, and fastening. The thirty-six-cornered cross section includestwenty-four internal angles and twelve external angles disposed betweenthirty-six sides. Each of the internal angles and the external anglesare at least 45 degrees and are less than 180 degrees.

Thirty-six-cornered cross sections in accordance with the presentdisclosure may, therefore, allow improved impact energy management over,for example, basic polygonal strengthening member cross sections,including basic twenty-sided polygonal cross sections, while minimizingmass per unit length.

Thus, as illustrated, strengthening members in accordance with thepresent disclosure are configured to achieve strength increases (i.e.,load carrying and energy absorption) over basic polygonal designs(including polygonal strengthening member cross sections having the samenumber of sides), while also permitting flexibility in design to bettermeet vehicle space requirements. Such strengthening members may,therefore, be used to replace existing strengthening member crosssection designs (both traditional and non-traditional).

Various exemplary approaches of the present disclosure contemplate, forexample, strengthening members with corners having different bend radii,with non-uniform cross sections (e.g., having non-symmetrical shapes),and/or with sides having variable thicknesses (i.e., having taperedsides). Various additional exemplary approaches contemplatestrengthening members that are bent and/or curved. Moreover, to furtheradjust a member's folding pattern and/or peak load capacity, variousadditional exemplary approaches also contemplate strengthening membershaving trigger holes, flanges, and/or convolutions as would beunderstood by those of ordinary skill in the art.

Furthermore, multi-cornered strengthening members in accordance with thepresent disclosure are contemplated for use with a number of structuralmembers, such as, for example, crush cans, front rails, mid-rails, rearrails, side rails, shotguns, cross members, roof structures, beltlinetubes, door beams, pillars, internal reinforcements, and othercomponents that can benefit from increased crash energy absorption. Inaddition, such strengthening members can be applied to bothbody-on-frame and unitized vehicles, or other types of structures. Thus,depending on application, strengthening members may have varied shapes(i.e. various cross sections) to accommodate specific member spaceconstraints. When used as a vehicle front rail, for example, to achieveoptimized axial crush performance, the lengths and thicknesses of thesides and/or angles of the corners can all be adjusted (tuned) toprovide optimal strength, size and shape to meet engine compartmentconstraints.

Although various exemplary approaches described herein have beendescribed as configured to be used with automotive vehicles, it isenvisioned that the various strengthening members in accordance with thepresent disclosure may be configured for use with other types ofvehicles and/or structures, for which it may be desirable to provideincreased load carrying capacity, crash energy absorption, and bendingresistance. Thus, it will be appreciated by those of ordinary skill inthe art having the benefit of this disclosure that the presentdisclosure provides strengthening members for various applications.Further modifications and alternative embodiments of various aspects ofthe present disclosure will be apparent to those skilled in the art inview of this description.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms encompassed by the claims.The words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the disclosure. Aspreviously described, the features of various embodiments may becombined to form further embodiments of the invention that may not beexplicitly described or illustrated. While various embodiments couldhave been described as providing advantages or being preferred overother embodiments or prior art implementations with respect to one ormore desired characteristics, those of ordinary skill in the artrecognize that one or more features or characteristics may becompromised to achieve desired overall system attributes, which dependon the specific application and implementation. These attributes mayinclude, but are not limited to cost, strength, durability, life cyclecost, marketability, appearance, packaging, size, serviceability,weight, manufacturability, ease of assembly, etc. As such, embodimentsdescribed as less desirable than other embodiments or prior artimplementations with respect to one or more characteristics are notoutside the scope of the disclosure and may be desirable for particularapplications.

What is claimed is:
 1. A strengthening member for an automotive vehicle,the strengthening member comprising: a thirty-six-cornered cross sectionhaving adjacent sides defining internal angles and external angles;wherein each of the internal angles and the external angles is at least45 degrees and is less than 180 degrees, wherein the sides define aplurality of adjacent lobes disposed about a perimeter of thestrengthening member, and wherein, along the perimeter of thethirty-six-cornered cross section, individual lobes of the plurality oflobes are separated by one external angle and include six internalangles and two external angles.
 2. The strengthening member of claim 1,wherein individual lobes of the plurality of lobes include one side wallextending in a plane parallel to a first axis, two side walls extendingin planes parallel to a second axis perpendicular to the first axis, andsix side walls extending in planes disposed at a non-zero angle relativeto the first axis.
 3. The strengthening member of claim 1, wherein thethirty-six-cornered cross section defines twenty-four internal anglesand twelve external angles.
 4. The strengthening member of claim 3,wherein the twenty-four internal angles are greater than 90 degrees andthe twelve external angles are approximately equal to 90 degrees.
 5. Thestrengthening member of claim 3, wherein the twenty-four internal anglesare greater than 90 degrees and the twelve external angles are greaterthan 90 degrees.
 6. The strengthening member of claim 1, wherein each ofthe sides has a length ranging from about 10 mm to about 250 mm.
 7. Thestrengthening member of claim 1, wherein a thickness of the sides andcorners ranges from about 0.7 mm to about 6.0 mm.
 8. The strengtheningmember of claim 1, wherein corners of the thirty-six-cornered crosssection have substantially the same thickness as the sides of the crosssection.
 9. The strengthening member of claim 1, wherein thestrengthening member has a continuous taper along a substantial lengthof the strengthening member from a first end of the strengthening memberto a second end of the strengthening member.
 10. The strengtheningmember of claim 1, wherein a first side wall of a first lobe is spaced afirst distance from a second side wall of a second lobe adjacent to thefirst lobe along the perimeter, wherein a third side wall of the firstlobe is spaced a second distance from a fourth side wall of a third lobeadjacent to the first lobe along the perimeter, and wherein the firstdistance is greater than the second distance.
 11. A strengthening memberfor an automotive vehicle, comprising: a thirty-six-cornered crosssection having thirty-six sides and defining twenty-four internal anglesand twelve external angles, wherein the cross section defines fouradjacent lobes disposed about a central axis, wherein each lobe definessix internal angles and two external angles, and wherein, along aperimeter of the cross section, adjacent lobes define one external angledisposed therebetween.
 12. The strengthening member of claim 11, whereineach of the internal angles and the external angles is at least 45degrees and less than 180 degrees.
 13. The strengthening member of claim11, wherein the one external angle disposed between adjacent lobes isapproximately 90 degrees.
 14. The strengthening member of claim 11,wherein the one external angle disposed between adjacent lobes is lessthan 90 degrees.